Blind Quantum Computation Research Articles

Effective Agent Quantum Private Data Query against Malicious Joint Attack with Blind Quantum Computing

Effective Agent Quantum Private Data Query against Malicious Joint Attack with Blind Quantum Computing

The brickwork state with fewer qubits in blind quantum computation

The brickwork state with fewer qubits in blind quantum computation

Benchmarking of quantum protocols

Quantum network protocols offer new functionalities such as enhanced security to communication and computational systems. Despite the rapid progress in quantum hardware, it has not yet reached a level of maturity that enables execution of many quantum protocols in practical settings. To develop quantum protocols in real world, it is necessary to examine their performance considering the imperfections in their practical implementation using simulation platforms. In this paper, we consider several quantum protocols that enable promising functionalities and services in near-future quantum networks. The protocols are chosen from both areas of quantum communication and quantum computation as follows: quantum money, W-state based anonymous transmission, verifiable blind quantum computation, and quantum digital signature. We use NetSquid simulation platform to evaluate the effect of various sources of noise on the performance of these protocols, considering different figures of merit. We find that to enable quantum money protocol, the decoherence time constant of the quantum memory must be at least three times the storage time of qubits. Furthermore, our simulation results for the w-state based anonymous transmission protocol show that to achieve an average fidelity above 0.8 in this protocol, the storage time of sender’s and receiver’s particles in the quantum memory must be less than half of the decoherence time constant of the quantum memory. We have also investigated the effect of gate imperfections on the performance of verifiable blind quantum computation. We find that with our chosen parameters, if the depolarizing probability of quantum gates is equal to or greater than 0.05, the security of the protocol cannot be guaranteed. Lastly, our simulation results for quantum digital signature protocol show that channel loss has a significant effect on the probability of repudiation.

Fully device-independent model on quantum networks

The Bell inequality can provide a useful witness for device-independent applications with quantum (or postquantum) eavesdroppers. This feature holds only for single entangled systems. Our goal is to explore a device-independent model for quantum networks. We first propose a Bell inequality to verify the genuinely multipartite nonlocality of connected quantum networks including cyclic networks and universal quantum computational resources for a measurement-based computation model. This is further used to construct a monogamy relation in a fully device-independent model with multisource quantum resources. It is finally applied for multiparty quantum key distribution, blind quantum computation, and quantum secret sharing. The present model can inspire various large-scale applications on quantum networks in a device-independent manner.

Multi-server blind quantum computation protocol with limited classical communication among servers

A user who does not have a quantum computer but wants to perform quantum computations may delegate his computation to a quantum cloud server. In order that the delegation works, it must be assured that no evil server can obtain any important information on the computation. The blind protocol was proposed as a way for the user to protect his information from the unauthorized actions of the server. Among the blind protocols proposed thus far, a protocol with two servers sharing entanglement, while it does not require to a user any quantum resource, does not allow the servers to communicate even after the computation. In this paper, we propose a protocol, by extend this two-server protocol to multiple servers, which remains secure even if some servers communicate with each other after the computation. Dummy gates and a circuit modeled after brickwork states play a crucial role in the new protocol.

Variational secure cloud quantum computing

Variational quantum algorithms (VQAs) have been considered to be useful applications of noisy intermediate-scale quantum (NISQ) devices. Typically, in the VQAs, a parametrized ansatz circuit is used to generate a trial wave function, and the parameters are optimized to minimize a cost function. On the other hand, blind quantum computing (BQC) has been studied in order to provide the quantum algorithm with security by using cloud networks. A client with a limited ability to perform quantum operations hopes to have access to a quantum computer of a server, and BQC allows the client to use the server's computer without leakage of the client's information (such as input, running quantum algorithms, and output) to the server. However, BQC is designed for fault-tolerant quantum computing, and this requires many ancillary qubits, which may not be suitable for NISQ devices. Here, we propose an efficient way to implement the NISQ computing with guaranteed security for the client. In our architecture, only N+ 1 qubits are required, under an assumption that the form of ansatzes is known to the server, where N denotes the necessary number of the qubits in the original NISQ algorithms. The client only performs single-qubit measurements on an ancillary qubit sent from the server, and the measurement angles can specify the parameters for the ansatzes of the NISQ algorithms. No-signaling principle guarantees that neither parameters chosen by the client nor the outputs of the algorithm are leaked to the server. This work paves the way for new applications of NISQ devices.

A Modified Key Sifting Scheme With Artificial Neural Network Based Key Reconciliation Analysis in Quantum Cryptography

Quantum Cryptography emerged from the limitations of classical cryptography. It will play a vital role in information security after the availability of expected powerful quantum computers. Still many quantum primitives like quantum money, blind quantum computation, quantum copy protection, etc. are theoretical as they require a completely functional quantum computer for their implementation. But one prominent quantum cryptographic primitive, the Quantum Key Distribution (QKD) is possible with current technology. The QKD is a key establishment system having several stages namely raw key generation, key sifting, key reconciliation, and privacy amplification. In this paper, an efficient key sifting scheme has been developed. Successful simulation has shown that the proposed modified key sifting scheme requires less time to build the sifted key compared to the sifted key in conventional BB84 protocol in most cases. This paper also represents Tree Parity Machine (TPM) based key reconciliation analysis using different learning algorithms such as Hebbian, Anti-Hebbian, and Random-Walk. This reconciliation analysis helps to choose the optimum learning algorithm for Artificial Neural Network (ANN) based key reconciliation in future Quantum Key Distribution systems.

Measurement-based universal blind quantum computation with minor resources

Blind quantum computation (BQC) enables a client with less quantum computational ability to delegate her quantum computation to a server with strong quantum computational power while preserving the client's privacy. Generally, many-qubit entangled states are often used to complete BQC tasks. But for a large-scale entangled state, it is difficult to be described since its Hilbert space dimension is increasing exponentially. Furthermore, the number of entangled qubits is limited in experiment of existing works. To tackle this problem, in this paper we propose a universal BQC protocol based on measurement with minor resources, where the trap technology is adopted to verify correctness of the server's measurement outcomes during computation and testing process. In our model there are two participants, a client who prepares initial single-qubit states and a server that performs universal quantum computation. The client is almost classical since she does not require any quantum computational power, quantum memory. To realize the client's universal BQC, we construct an $m\times n$ latticed state composed of six-qubit cluster states and eight-qubit cluster states, which needs less qubits than the brickwork state. Finally, we analyze and prove the blindness, correctness, universality and verifiability of our proposed BQC protocol.

Blind Quantum Computation Using a Circuit-Based Quantum Computer

When a universal quantum computer is used by the public, it is assumed that it will be in the form of a quantum cloud server that exists in a few bases due to its cost. In this cloud server, privacy will be a crucial issue, and a blind quantum computation protocol will be necessary so that each user can use the server without the details of the calculations being revealed. It is also important to be able to verify that the server is performing calculations as instructed by the user, since quantum calculations cannot be verified by classical computation. In this paper, we put forward a protocol that achieves blindness using the quantum one-time pad for encryption and a T-like gate, and while verifying computation using trap qubits.

Blind three-qubit exact Grover search on a nitrogen-vacancy-center platform

Here we put into practice the concept of blind client-server quantum computation, in which a client with limited quantum power controls the execution of a quantum computation on a powerful server, without revealing any details of the computation. In particular, it is a three-node setting in which an oracular quantum computation can be executed blindly. In this Blind Oracular Quantum Computation (BOQC), the oracle (Oscar) is another node, with limited power, who acts in cooperation with the client (Alice) to supply quantum information to the server so that the oracle part of the quantum computation can also be executed blindly. We develop tests of this protocol using two- and three-qubit versions of the exact Grover algorithm (i.e., with database sizes $4\ensuremath{\le}N\ensuremath{\le}8$), obtaining optimal implementations of these algorithms within a gate array scheme and the blinded cluster-state scheme. We discuss the feasibility of executing these protocols in state-of-the-art three-node experiments using nitrogen-vacancy diamond electronic and nuclear qubits.

Universal single-server blind quantum computation for classical clients

Blind quantum computation (BQC) allows a client without enough quantum technologies to delegate her quantum computation to a remote quantum server, while keeping her input, output and algorithm secure. In this paper, we propose a universal single-server and almost-classical-client BQC protocol. In this protocol, the client interfaces with only one server and the only ability of the client required is to get particles from the trusted center and forward them to the server. We present an analysis of this protocol and modify it to a universal single-server and fully-classical-client BQC protocol by improving the ability of the trusted center. Based on our protocols and recent works, a new ‘Cloud + Certificate Authority (CA)’ style is proposed for the BQC.

Analysis and improvement of verifiable blind quantum computation

In blind quantum computation (BQC), a client with weak quantum computation capabilities is allowed to delegate its quantum computation tasks to a server with powerful quantum computation capabilities, and the inputs, algorithms and outputs of the quantum computation are confidential to the server. Verifiability refers to the ability of the client to verify with a certain probability whether the server has executed the protocol correctly and can be realized by introducing trap qubits into the computation graph state to detect server deception. The existing verifiable universal BQC protocols are analyzed and compared in detail. The XTH protocol (proposed by Xu Q S, Tan X Q, Huang R in 2020), a recent improvement protocol of verifiable universal BQC, uses a sandglass-like graph state to further decrease resource expenditure and enhance verification capability. However, the XTH protocol has two shortcomings: limitations in the coloring scheme and a high probability of accepting an incorrect computation result. In this paper, we present an improved version of the XTH protocol, which revises the limitations of the original coloring scheme and further improves the verification ability. The analysis demonstrates that the resource expenditure is the same as for the XTH protocol, while the probability of accepting the wrong computation result is reduced from the original minimum (0.866) d* to (0.819) d*, where d* is the number of repeated executions of the protocol.

Verification of blind quantum computation with entanglement witnesses

Verifiable blind quantum computation provides a cloud scenario for scalable quantum information processing. However, constructing one resource-efficient verification protocol is still an open problem. In this paper, the context of verification we consider is the measurement-based model, in which the client receives the graph state prepared by the server and performs single-qubit measurements on it to drive the computation. We first utilize three entanglement witnesses to estimate the fidelity of the prepared graph state. Applying entanglement witnesses to design the test phase, we propose verification protocols. Our protocol requires overhead in terms of copies of the graph state that scales as $O({n}^{2}logn)$, where $n$ is the number of qubits of the graph state. Furthermore, the soundness of our protocol is improved. The advantages of our protocol are derived from the fact that each entanglement witness can be implemented by the client with a fixed number of measurement settings.

Blind oracular quantum computation

In the standard oracle model, an oracle efficiently evaluates an unknown classical function independent of the quantum algorithm itself. Quantum algorithms have a complex interrelationship to their oracles; for example the possibility of quantum speedup is affected by the manner by which oracles are implemented. Therefore, it is physically meaningful to separate oracles from their quantum algorithms, and we introduce one such separation here. We define the blind oracular quantum computation (BOQC) scheme, in which the oracle is a distinct node in a quantum network. Our work augments the client–server setting of quantum computing, in which a powerful quantum computer server is available on the network for discreet use by clients on the network with low quantum power. In BOQC, an oracle is another client that cooperates with the main client so that an oracular quantum algorithm is run on the server. The cooperation between the main client and the oracle takes place (almost) without communication. We prove BOQC to be blind: the server cannot learn anything about the clients’ computation. This proof is performed within the composable security definitions provided by the formalism of abstract cryptography. We enhance the BOQC scheme to be runnable with minimal physical qubits when run on a solid-state quantum network; we prove that this scheme, which we refer to as BOQCo (BOQC-optimized), possesses the same security as BOQC.

Quantum federated learning through blind quantum computing

Private distributed learning studies the problem of how multiple distributed entities collaboratively train a shared deep network with their private data unrevealed. With the security provided by the protocols of blind quantum computation, the cooperation between quantum physics and machine learning may lead to unparalleled prospect for solving private distributed learning tasks. In this paper, we introduce a quantum protocol for distributed learning that is able to utilize the computational power of the remote quantum servers while keeping the private data safe. For concreteness, we first introduce a protocol for private single-party delegated training of variational quantum classifiers based on blind quantum computing and then extend this protocol to multiparty private distributed learning incorporated with differential privacy. We carry out extensive numerical simulations with different real-life datasets and encoding strategies to benchmark the effectiveness of our protocol. We find that our protocol is robust to experimental imperfections and is secure under the gradient attack after the incorporation of differential privacy. Our results show the potential for handling computationally expensive distributed learning tasks with privacy guarantees, thus providing a valuable guide for exploring quantum advantages from the security perspective in the field of machine learning with real-life applications.

Secure quantum fog computing model based on blind quantum computation

Secure quantum fog computing model based on blind quantum computation

Blinding quantum computation using alternative sources

Quantum computation has seen rapid progress in the past years. Due to implementation complexity and cost, cloud-based quantum computing is strongly believed to be the most feasible framework for individual users. Universal blind quantum computing (UBQC) provides the protocol for secure delegation of arbitrary quantum computations and has received significant attention. However, one of the major challenges in UBQC is a secure and reliable transmission of a quantum state over a long distance. Herein, we improve the efficiency of UBQC using alternative photon sources. Our analysis shows that a heralded single-photon source can significantly improve the transmitted distance of UBQC and a modified coherent source can reduce the required transmitted number of pulses. Furthermore, we study the finite-data-size effect, which is a crucial for real-world applications. Our proposed scheme can be a promising alternative for the future development of UBQC.

Verifiable Multi‐Party Universal Blind Quantum Computing in Distributed Networks

Blind quantum computing (BQC) ensures that a classical client could delegate complex computing tasks to a remote quantum server safely. In order to detect the dishonest behavior of the participants, we present a verifiable multi-party universal BQC protocol in distributed networks. By using the stabilizer formalism, we propose an honesty check method to test the correctness of the graph states generated by the servers. The honesty of both the clients and the servers can be judged fairly with the help of the arbitrator. Moreover, a load balancer is introduced to control the possible breakdown of servers in the network. No-signaling principle ensures the unconditional security of the protocol. Through the use of universal resource states, our protocol can be applied in more multi-party verifiable universal BQC protocols. The failure management and workload balancing of the protocol also provide a promising prospect for the future BQC network.

Blind quantum computation where a user only performs single-qubit gates

Blind quantum computation (BQC) allows a user who has limited quantum ability to complete a quantum computational task with the aid of a remote quantum server, such that the user’s input, output, and even the algorithm can be kept hidden from the server. Up to now, there are mainly two models of BQC. One is that the client just needs the ability to prepare single qubits initiated by Broadbent, Fitzsimons, and Kashefi and the other is that the client only needs to perform single-qubit measurements first given by Morimae. In this paper, we put forward a new model of BQC in which a user only requires implementing a few single-qubit gates. We also propose a specific BQC protocol where a user only needs to implement two kinds of single-qubit gates to show the feasibility of the presented model and thus answer positively the open question whether a verified BQC protocol that only requires single-qubit gates for the user can be designed. This circuit model is quite flexible since various users with the ability to perform different single-qubit gates may all have the chance to achieve BQC. Furthermore, compared with the other two models, it may be more suitable for practical implementation in some experimental setups such as trapped ions and superconducting systems since the single-qubit gates are the most exact operations in such systems.

Multi-party blind quantum computation protocol with mutual authentication in network

Blind quantum computation (BQC) can ensure a client with limited quantum capability safely delegates computing tasks to a remote quantum server. In order to resist attacks from ignoring identity authentication in BQC protocols, it is necessary to guarantee the legality of both clients and servers in a multi-party BQC network. So we propose a multi-party BQC protocol involving three phases to distribute shared keys and authenticate identities. Firstly, by using the advantages of measurement device independent quantum key distribution (MDI-QKD), the registered client and the assigned server could share the initial key safely in registration phase. Secondly, with the help of semi-honest certificate authority (CA), mutual identity authentication phase realizes the two-way authentication from both sides through the shared key simultaneously. Thirdly, in the blind quantum computing phase, a registered client can complete his computing task by just measuring the qubits from the assigned server rather than preparing the qubits. Moreover, combined with first-in-first-out (FIFO) principle, clients’ authentication and blind quantum computing can be processed in parallel. The protocol can also be applied in other multi-party BQC protocols with the universality of resource states. Compared with other BQC protocols, the reliability of the protocol with identity authentication is guaranteed, and the efficiency will be significantly reflected in real experiments.